Description of the problem, including code/CLI snippet

The project.protectedbranches.create() method currently does not allow me to configure specific users push and merge rules. Is that hard to add?

GitLab API docs show how to add a user to a protected branch.

Expected Behavior

Able to set users to be able to merge/push to the protected branch.

Actual Behavior

No option

Specifications

• python-gitlab version: 1.6.0
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 11.2